Actinin



Actinin attaches the protein actin to the Z-lines in skeletal muscle cells and to dense bodies in smooth muscle cells. Both ends of actinin contain an actin-binding domain (ABD). Actinin is encoded by different genes. ACTN1 encodes α-actinin-1 (aA1) which is a cytoskeletal isoform. ACTN2 encodes an isoform aA2 found in cardiac and skeletal muscles. ACTN3 encodes aA3 which anchors actin at the muscle Z-disk. ACTN4 encodes aA4 which is found in the cytoplasm and is thought to be involved in metastasis. Actinins contain a 3-helix bundle which is called spectrin repeat (SR). The images at the left and at the right correspond to one representative Actinin, i.e. the crystal structure of human Alpha-actinin-1 (2eyi).

α-actinin-1 (aA1)
2eyi, 2eyn - haA1 ABD – human

α-actinin-2 (aA2)
1h8b – haA2 EF hands+rTitin Z-repeat – rabbit

1hc2, 1quu – haA2 SR

1hci – haA2 repeats 1-4

α-actinin-3 (aA3)
3lue – haA3+hActin

1tjt, 1wku – haA3 ABD

1g8x – aA3 1-2 repeats/myosin II heavy chain – Dictyostelium discoideum

α-actinin-4 (aA4)
2r0o – haA4 ABD (mutant)

1wlx – haA4 SR – NMR

1sjj – aA – chicken - cryoEM